Systems and methods are provided for handling different timing advance (TA) adjustment delays corresponding to different transmission time intervals (TTIs) from different serving cells under carrier aggregation or dual connectivity. A user equipment (UE) selects and implements one TA adjustment delay even if two or more serving cells transmit with different TTIs. In one embodiment, the UE uses a predetermined TA adjustment delay for each of a plurality of TA commands received from serving cells with different TTI lengths. In another embodiment, the UE uses a TA adjustment delay that is a maximum value of the TA adjustment delays for the TTIs from the different serving cells.